This invention relates to a hydrocracking process and is particularly concerned with the use of a hydrocracking catalyst containing a crystalline, nonzeolitic molecular sieve to produce high octane gasoline.
Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel and other middle distillate products, as well as lower boiling liquids, such as naphtha and gasoline, by hydrocracking a hydrocarbon feedstock derived from crude oil. Feedstocks most often subjected to hydrocracking are gas oils and heavy gas oils recovered from crude oil by distillation. A typical gas oil comprises a substantial proportion of hydrocarbon components boiling above about 700.degree. F., usually at least about 50 percent by weight boiling above about 700.degree. F. A typical heavy gas oil normally has a boiling point range between about 600.degree. F. and 1050.degree. F.
Hydrocracking is generally accomplished by contacting, in an appropriate reaction vessel, the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen so as to yield a product containing a distribution of hydrocarbon products desired by the refiner. Although the operating conditions within a hydrocracking reactor have some influence on the yield of the products, the hydrocracking catalyst is the prime factor in determining such yields. Typical hydrocracking catalysts for producing gasoline from gas oils and similar feedstocks are normally composed of one or more Group VIB or Group VIII metals on a support containing a zeolite having catalytic cracking activity. The octane of the gasoline produced using such catalysts has traditionally been increased by adding lead compounds to the gasoline product. Unfortunately, recent environmental legislation has restricted the use of lead additives to the extent that refiners now have difficulty producing gasoline having a sufficiently high octane number. And, when catalysts are formulated to produce higher octane gasolines to compensate for the fact that lead additives cannot be used, the catalysts quite frequently are less active than typical hydrocracking catalysts.
Accordingly, it is one of the objects of the present invention to provide a process in which the hydrocracking catalyst has a high activity for hydrocracking and produces a gasoline having a relatively high octane number. This and other objects of the invention will become more apparent in view of the following description of the invention.